Closed loop trouble

[Jessbo]

I am having trouble with my new closed loops. I have one on either side of my 125 gal. reef tank. Left side uses a mag 12, right uses mag 18. Problem is, both pumps makes alot of noise. I ran the pumps alone in a bucket and were completely silent. But unless I close off my valves almost all the way, they are way loud! I increased the inlet piping to 1" thinking the inlet was restricted, but no change in noise level at all. The left side(mag 12)supplies a 3/4" bulkhead, and a 1/2" spraybar at the back of my tank. Problem with that is, I only get flow through the bulkhead, not the spraybars. I blocked off the bulkhead and get VERY LITTLE flow through the bars. I used a T to supply the output to the bulkhead and spraybars. Right after the tee I reduced the line to 1/2" flexible tubing. Goes up to the top of tank, the down the back wall. Think I should increase the line to 3/4" all the way up my tank, only reducing to 1/2" when it reached spraybars themselves. Look at my rough sketches, see what you all think. Please help!!!!!

 

[reedman]

The problem with spraybars is that they require a lot of pressure to make them work well. I would recommend going with an outlet either pointing straight down the middle back of the tank or one or two pointing across the back to sweep the detritus toward the front where it can be put into suspension or syphoned out.

What's happening with your plumbing is that fluid wants to take the path of least resistance. In this case it's easier to flow through a 3/4" pipe than a 1/2" pipe. If you are going to run a spray bar I would take the mag 18 and use it to power the spray bar and use the other pump to run the outlets. Then you won't have the balancing act.

Mags can be noisy. They will resonate sound through anything thay are in direct contact with, including hard plumbing. I would recommend resting the pump itself on some kind of pad (mouse pad or similar) and using flexible plumbing to plumb it. This will cut down on the noise a lot.

 

[Jessbo]

I was thinking of putting the pumps themselves underneath the aquarium. I have heard that when you draw water from the tank itself, that I cancels out the head pressure the pump has to overcome pumping it back up due to gravity's help. Is this true? Maybe just put them under tank rather than along side. I wanted to use the mag 18 for the right side since that will be my sps side(more flow), the mag 12 on the other for lps. I am considering just two outlets aimed down that back wall, hopefully pushing everything away from the back wall. Spraybar, just doesn't seem practicle now. But am going to change the supply line back to 3/4", only leaving the spraybars themselves 1/2", might work better. I used flexible tubing on the 12 first, noise lessened a little, but still present. Tried it on the 18, but noise level didn't change a bit. From what I can tell, the noise is coming right when the water comes into the pump, or at the impeller itself. That is why I think the input flow might be restricted. But when I start closing the valves, the pump gets quieter. More restriction, less noise????????? Just thinking these larger pumps are just louder than my mag 9.5, which is whisper silent. What about how the water is being fed to the pumps? Look at my pics, and see if they are too restrictive. Doesn't seem like it would make a problem, but I am trying every option. Just want the noise to stop!!!!!!!

 

[reedman]

I have heard that when you draw water from the tank itself, that I cancels out the head pressure the pump has to overcome pumping it back up due to gravity's help. Is this true?

This is largely true. You shouldn't see any drop in output from putting the pump under the tank. If you add any elbows to do this though, you will see a drop.

I am considering just two outlets aimed down that back wall, hopefully pushing everything away from the back wall.

Just for reference I have one output doing this on my 75 and I have zero detritus in the back. This is the best configuration I have found.

Noise: I would recommend nothing smaller than 3/4" until you get to the tank itself. On the input side don't drop below 3/4" anywhere. If it is noise like air and water mixing then the pump may be cavitating a bit due to not enough supply. This would be consistent with the fact that when you restrict the flow (less input needed) the pump quiets. To solve this you may need to up the input plumbing to 1" and just reduce it at the pump.

Do keep in mind though that Mags are not silent pumps. They make noise and the bigger they are the more noise they make. If you want silent check into something like the sequence pumps, dolphin, or eheim. They all run very quiet, pull less power per gallon pumped, and run cool.

 

[Jessbo]

I think I have decided to put the pumps below, using 1" for the inputs. With the 3-4 foot drop should allow plenty of flow in. Going to use flexible tubing from the pump and out of the stand, then switched to hard pvc to the bulkheads. So for the outputs at the back, where do you recommend they be placed at? Just below the water line aiming straight down, or down a bit?

 

[reedman]

That really depends on your tanks aquascape. Mine is at the top of the tank pointing down. This does 2 things for me. (1) less plumbing in the tank (2) more spread of flow before it hits the bottom. works well in my tank.